Telephone-exchange system



-S. B. WILLIAMS, Jn. TELEPHONE EXCHANGE SYSTEM.

APPLICATION man ma e. 8, 1919.

1,393,728. Patented 0ct.'11,1921

' HEW hmwfan' Jhmwe/ 5. Mlfl'ama Jr.

S. B. WILLIAMS, JR.

TELEPHONE EXCHANGE SYSTEM.

APPLlCATlON FILED 050.8. 1919.

1,393,728, Patented Oct. 11, 1921.

uww R U llll s. B. WILLI AMS, JR.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC. 8, I919.

I Patented 00t- 11,

7 SHEETSSHEET 4L hue/mar: Jamue/ 5, MW/ams/k y W y S. B. WILLIAMS, JR.

IELEPHONE EXCHANGE SYSTEM. APPLICATION FILED DEC.8. 1919.

1,393,728 Patented Oct. 11, 1921-,

7 SHEETS-SHEET 5- 7 van far. Sa/m/e/ 5 W/Y/mmsJn & 4 Ai/y S. H. WILLIAMS, JR. TELEPHONE EXKLHANGE SYSTEM.

APPLICATION FILED DEC. 8, I919.

Patented 0ct.11,19 21.-

1 SHEETS-SHEET 6.

S. B. WILLIAMS, JR. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED 050.8, 1919.

1,393,728. Patented Oct. 11, 1921.

1 SHEETS-SHEET I.

1.2.4. 5. 6.8. m. I I2. I4. I8.

' lector switch.

UNITED srarfssearnur o F cE.

SAMUEL B. winner/rs,- 3a., or nncoir'nrn,

'rnrc ooMr'ANY, INCORPORATED, or 'Y ORK'. I

1,393,728. Specification Application filed December 8, 1919.

To all whomz't may coacerm.

Be it known that I, SAM EL B. lVinmaars, Jr., a citizen of theUnited States, residing at Brooklyn, in the county of Kings, State of New York, have invented certain new and useful Improvements in Telephonedilxchange Systems, of whichithe following is a full, clear, concise, and exact description.

This; 1nvent1on relates to telephone exchange systems and more particularly to systems of the type employing automatic switches for establishlng talking connections between subscribers lines.

Telephone exchange systems whether of the full automatic or semi-automatic type may be briefly considered as consisting of two-distinct classes, so far as concerns the method in which the preliminary switching operations-involved in the establishment of a connection are elfected automatically as a result of the usual act of removing the re ceiver from the switchhook upon the initiation of a call. In systems of one of these classes it is the practice to have the telephone line of each subscriber to an exchange terminate in a line or individual switch. These switches are arranged to have access to trunk circuits leading to a plurality of selector switches and may becontrolled by automatic devices in such manner that the' individual switch of each line when not in use is constantly maintained in operative relation-to a'trunk which leads to an idle selector switch. When a subscriber, desiring to connect his line with the line of some other subscriber, removes his receiver from the hook, theline switch individual to his line, being thus prepositioned before anidle to con nect his line directly through to a first se- The subscriber may then begin to transmit impulses immediatelyafter initiating the call with the assurance that such impulseswill be properly directed to the circult extending switching mechanism.

ll hile systems involving the use of indi-' vidual switches possess the desirable feature of immedlate connection to idle trunks,

and the incident insurance against impulse mutilation, there is this undesirable factor to be considered, that comparatively large number of switches isrequired.

In the other systems, above alluded to, the subscribers lines, instead of each being provided with of Letters Patent.

, multiple condition is class ofautomatic switching nnw'roraxj assrenon ro vvissriinn' ELEC- A oonrona'rrolvor NEW,

'IELEPHQNE-EXCHANGE SYSTEM.

. I PatentedOct. 11, 1-921.

7 Serial No. 343,284.

an individual switch are terminatedin the contacts of line finder switches. These finder switches maybe arranged to serve any one of a large number of calling lines. When a subscriberinitiat es a call, a placed u on his line such that a finder having accessthe reto isset in operation to connect with the calling line and extend thesame to an idle selector switch. After the finder has completedits functionthe calling party may then transl mit impulses to selectively operate the se lector switches in the proper manner. By the employment of finder switches each serving a relatively large number of lines, it is evident that a considerable saving may be realized in the necessary amount of switching mechanism. But at the same time, the saving in the number of switches madepossible by the use of line finders may only be had'by sacrificing to someextent the desirable featureof immediate con nection of calling lines to idle trunks, and there is, therefore, the liability of switches being improperly operated'as a result of the calling subscriber commencing to send out impulses before the finder hasf'had time to complete its function. I

With the foregoing inview, the present invention has as its general object'the provision of an automatic telephone system, so constructed and arranged as to embody the advantageous features of the above described methods of switching calling} lines into connection with idle trunk circuits, and at the same time one which practically switches are selectively controlled W eliminates the undesirable features 'of,both.-- More specifically the, object of the invenfor quickly associating such mecha'nism with a calling said line. I J

A feature of the invention res1desin the line when a call isinitiated upon provision of means, in a system comprising 7 a line finder and a series of directively con trolled select-or switches for extending calling lines together with a switch controlling mechanism adapted to beset by the calling subscriber to control said selector switches,"whereby said controlling mechanism is quickly associated with the calling line o'n the initiation of a call, and may be setby the calling subscriber while said ing line with the mechanism, whereby the mechanism is as-;

sociated with a calling line without delay and'beiore the calling subscriber commences to dial the number of the desired line, and in the provision of largecapacity switches for'subsequently establishing a connection with the controlling mechanism and through switches directly controlled by said mechanismto the line of a called subscriber.

A still'further feature resides in the pro vision ofa plurality of switch controlling mechanisms common to a group of sub scribers "lines, each comprising of registers for registering line numbers, whereby the designation of a desired line maybe registered on said registers which thereupon operate to directivcly control the selector switches of the system to extend line to the the connection" from the calling line'of the desired subscriber.

A still further feature resides in the provision ofmeans iEor directively controlling the movements of the line finder switch for'selecting a brush set'which has access to the subgrou'p'of lines inv which the calling lineis located, by the employment of a plurality or relays which normally function to control the operation of other non-directive switches with which they are associated. This feature enables the employment of a "line finder switch of the same type as the selector switches which are employed for further extending the line, and without the addition or extra equipment for selecting fileproper set of brushes.'

vention.

Such other features as are contemplated by the present invention will become more apparent from the following description and theappended claims. The invention will now be. described in connection with one specific embodiment of the genus of the in- In the accompanying drawings 2- Figure 1 shows one line of a main group of subscribers lines, a finder switch for making connections therewith, a district selector switch for extending connection from a subscribers line into a the exchange gand linked to the line finder switch, together with the associated cirfirst selector switch of the a plurality desired district of might be used.

slightly slow down the rapidity of line excuits and apparatus through the medium of whichthe switches are controlled;

Fig. 2 shows an incoming selector switch for further extending a subscribers line, together with the associated circuits for controlling it;

Fig. 3 shows a final selector or connector switch for completing a connection to a desired subscribers line together with the circuits and apparatus for controlling it, and one of a group of subscribersflines to which the final selector has access;

Fig. 4 shows a primary line finder switch for making a primary connection with a subgroup of subscribers lines together with the assoc ated circuits for controlling it;

nism or impulse register for registering impulses transmitted thereto through the .op-'- eration of a calling subscribers impulse sending dial; y

Fig. 7 shows the circuits of-an impulse sender which is operated in accordance with the setting oi the controlling mechanism disclosed'in Fig. 6; and

Fig. 8 shows diagrammatically, the manner in which the several figures of the draw ing are to be arranged to illustrate as much of a complete organization as is necessary to impart an understanding of the construc tion and mode of operation ofthe system.

General description ofappara-tus. A single telephone line of: amain group of 450 linesis shown in Fig. 1, it being understood that there are asmanygroups as are necessary to accommodate the lines ter-' minating in the exchange. The main groups a finder selector for selecting an of lines are preferably divided into fifteen subgroupsof thirty lines each, each such subgroup being served by a group of pri-f mary line finders having a capacity or thirty lines each, and are also divided intofive subgroups of ninety lines each, each subgroup oif ninety lines being served byone oi the brush sets of each main line finder having access thereto. It would of course "be pos sible to slightly change the manner of subgrouping by providing primary finder switches oi fifty-line capacity and by providing main line finders of 500 line capacity, whereby main line finders of standard type This would, however,

tension and would to that extent sacrifice some of the efiiciency-which this system is designed to attain. I

The line has associated with it at the central oiiice, aline relay 8 and a cut-off relay 9 and, being a line in an automatic exchange, is provided with the usual sending mechanism S. The line represented as a calling line A, in Fig.1, and the line shown as a called line B, in Fig; 3, maybe lines of the same type, similarly equipped but located at different exchanges or at the same exchange. In the present instance, the line shown in Fig. 3 is illustrated as one of a group of lines terminating in a private branch exchange and for that purpose is provided with a cut off relay 9 having iigh and low'resistance windings for 'cooperation'with testing circuits of the final selector switches which have access thereto. The line A, shown in Fig. 1, is illustrated'as provided with multiple terminals in the banks ofmain line finders LF and of primary line finders PLF, and with a starting circuit leadingthrough primary'line 'finder starting relays of all primary line finders having access to the subgroup of lines in which the line is located, the starting relays being common to all lines of the subgroup.

The groups of lines have access to' a plurality of selector controlling mechanisms or impulse registering devices through the medium of primary line finder switches PLF, secondary line finderswitches bLF, and register selectors RS shown in Figs. 4: and 5. In the particular system illustrated these switches are all of the well-known etc -bystep type in which a stepping pawl operates a ratchet wheel to which are connected brushes or wipers adapted to travel over the contacts of an arcuate terminal bank. These brushes or wipers are so arranged that for each step ofthe operating magnet, the brushes or wipers engage a corresponding set of terminals. The primary finder switches are each provided with five wipers and the secondary finder switches and register selectors are each provided with six wipers. These switches have no normal position but stop in whatever position they are placed by their respective operating magnets.

The main line finders and selector switches shown in Figs. 1, 2 and 3 are not novel in.

themselves and have therefore been shown merely diagrammatically. These switches are substantially like the switch illustrated and described in the patent to B. Craft and J. N. Reynolds No. 1,123,696, issued January 5, 1915. Each of these switches comprise a longitudinally movable shaft carrying as many sets of brushes 2 as there are groups of stationary terminals to be engaged. To move the shaft up, an extension at the lower end of the shaft is brought into engagement with a constantly rotating power roller 3 by means of an idler wheel operated set of brushes.

by theaip-drive magnet, and to move the shaft down, the extension is broughtinto engagement with the power roller i by means.

by the downdrive 2 are held apart so as to clear the bank ter-" minals associated therewith by means of a separating cam (not shown) located between the innermost brushes of the set. The brushes are tripped by means of a vertically disposed tripping spindle or rod 5 having disposed thereon a tripping finger 6 for each The spindlefi is rotated into tripping position by means of a single triping magnet. The trip rod in rotating, brings. all of the trip lingers 6 into position to operate the brush controlling cams of the corresponding sets of brushes, but only the brush set which has been positioned opposite its corresponding trip finger will be affected.

Each of the switches has associated with it, a commutator? which comprises a number of stationary commutatorsegments, and a set of movable wipers carried at the top of the switch shaft 1 and cooperating with the stationary segments. This commutator serves to make and break a number of controlling circuits in the various stagesof the longitudinal :mevement of the switch shaft.

The district selector DS is so arranged as to have three distinct upward movements, first a brush selectingmovement comprising five distinct steps, second aselecting movement for moving the selected brush set over the associated terminal bank comprising two steps, and third, a hunting movement over 7 the selected group of bank terminals. The

incoming selector switch 18 similarly has three movements, the group selecting movement of the selected set of brushes compris ing four steps. The connector switch differs slightly in construction from the other selector switches in that provision is made for driving the switch shaftupwardly at either a high speedthrough the high speed power roller 10 or at a slower speed through the slow speed roller 3. The switch shaft is driven upwardly I in three selective movements, first, a high speed movementfor se looting a set of-brushes corresponding to the group of 100 lines, in which the desired line is located; second, a high speedmovement for 'selecting'the particular subgroup of 10 lines, in which the line is located; and third, a slow speed upward movement for selecting the line in the subgroup of 10. If the desired line is one terminating in a private branch exchange, the switch may make a fourth upward movement which is a slow speed hunting movement.

The hnder selector shown in Fig. 5 is also of the power-driven type and substantially likethe switch shown in the patent to E. B-

Craft-and J. N. Reynolds hereinbefore referred to,

brushes is required, the brush selecting or tripping mechanism is omitted i i For controlling the circuits of hesystem, there are employed a number of sequence switches which are shown at diflerent points and are designated 100, 200, 300, 500, 600 and 700 respectively. These sequence switches may be of the type disclosed in Patent No. 1,127,808, issued February 9, 1915, to Reynolds and Baldwin. Each con sists of an electromagnetically controlled of associated switch springs.

springs associated with the sequence switch to 122 inclusive; those associated with the seque ce switch motor ordrivin mechanism and a number s) The switch 100 are designated 101 200 are designated 201 to inclusive; those associated with sequence itch 300 are designated 301 to inclusive; 'sociated with sequence switch 500 are designated 501 to; 519 inclusive; those associated with sequence switch 600 are designated 600 to 612 inclusive; and those associatedwith sequence switch 700 are designated 701 to v 0709 inclusive. sociated with the various To each of the contacts assequence switch applied certain numerals.

springs are in case of the cams 101,

These numerals,

201, 301, 501,601 and 701, indicate the only positions of the associates sequence switches in which these particular contacts are opened; the numerals applied to other contacts of each sequence switch dicate theionly positions of the p 'icular switch in which the associated contacts are closed and when the numerals are con nected'by the sign }-'the contacts are closed continuously between the positions indicated by the numerals so connected.

The controlling mechanism disclosed in Fig. 6 comprises a plurality of step-by-step all of the register switches each provided with a plurality of wipers arranged to be moved over associated banks of contacts, each bank of contacts, with the exception of the uppermost, comprising 10 contacts. These registors are arranged to be set in succession by impulses transmitted to their respective stepping ma nets over connections extenting to the line of a calling subscriber, the impulses being caused through the operation of the subscribers callingdial. 7

he sending mechanism shown in Fig; 7 and associated with the controlling mechan- V ism shown in Fig 6 is of the usual. type on lo in a series of 20 counting rela s. P e s :n a f Establishment of rcgzster.

The manner in which thesystem is or ganized will best be presented in connection with a description of the mode of its operation. It will be assumed that the subscriber at station but since only a single set of the line and through the the pilot alarm device those as through the left-hand armature .andback and front contact and thence to the test ture and front contact,

' circuit may initial connection to "idle stepping A initiates a call and desires to secure a connection with substation B in another exchange, the number of the desired subscriber being 45689. The removal of the receiver at substationA. closes a circuit for the line relay 8 which extends over armatures and back contacts of the cut-off relay 9. Line relay 8 becomes energized and at its armatureand frontcontact closes a circuit for the starting relay 400 common to the group of primary finder switches having access to the subgroup of the calling line. Relay 400 upon ener izing, closes a circuit at its outer left hand armature and front contact for (not shown) and at its inner left-hand armature and front vcontact, closes a circuit for relays 401 of all idle finders which extends from grounded battery, through the winding .of relay 401,

contact of relay 402, through the back contact and right-hand ,armatureof relay 403, and thence to ground at the inner left-hand armature and contact of relay 400. Relay 401, upon energizing, closes a circuit for relay 403 which extends from grounded battery, through the winding of this relay, through the left-hand armature and front contact of relay 401, through the back contact and right-hand "and thence to ground at the inner left-hand armature of relay 402,

armature and front contact of relay 400. Relay 403 thereupon establishes a locking circuit for itself over its left-hand armature brush 404. If the bank contact upon which this brush is resting atthe time, leads to a armature and back contact, opens the initial energizing circuit of re1ay401, andat its right-hand armature and back contact, opens the initial energizing circuit of relay 403. Relay 403, upon energizing, closes a circuit through the stepping magnet 406, which be traced from grounded battery, through the winding and interrupter contacts of magnet 406, through the front contact and right-hand armature of relay 403 and thence to ground at the inner lefthand armature and front contact of relay 400. Magnet 406 thereupon energizes, the brushes of the switch to the next set of bank terminals and interrupting its own energizing-circuit. If the set of bank terminals which the brushes of the switch now engage lead to a non-calling or busy line, the switch will take another step and will in this manner continue to move step-by-step until the brushes engage the multiple terminals of the calling line, when the test brush 404 will find no ground potential upon the test contact of the bank which it engages and the locking circuit of relay 403 will thereupon be destroyed. Relay 4023, upon deenergizing, opens at its righthand armature and front contact the circuit of the stepping magnet 406 and at its lefthand armature and back contact connects ground potential throughthe test brush 404 to the multiple test contacts of its bank to thereby mark the multiple test contacts of the calling line as busy for preventing other primary finder switches, which-have been simultaneously hunting for the terminals of the calling line, from making connection therewith. At its right-hand armature and back contact,-relay 403 established a circuit for the relay 412 which extends from grounded battery, through the left-hand winding of relay 412, through the front contact and left-hand armature of relay 402, through the back contact and right-hand armature of relay 403, and thence to ground at the inner left-hand armature and front contact of relay 400. 7

At the time relay 400 energized, a circuit was also established for the starting relay 521 for initiatingthe hunting movement of a secondary finder switch SLF and of a register selector RS. This circuit may be traced from grounded battery, through the winding of relay 521 and thence to ground at the front contact and outer right-hand armature of relay 400. "Upon energizing, relay 521 closes a circuit extending from ground, through the lower contact of sequence switch spring 502 (1), through the left-hand armature and front contact of relay 521, through the lower left-hand contact of sequence switch spring 503 (1) through the right-hand armature and back contact of relay 522, through the lower lefthand contact of sequence switch spring 504 (1). through the left-hand armature and back contact of relay 523, thence to grounded battery through the winding of relay 524. Relay 524 is energized in this circuit and at its left-hand armature closes a circuit for the relay 522 which extends from grounded battery, through the relay 522, through the lower left-hand contact of sequence switch spring 505 (1), through the front contact and left-hand armature of relay 524, through the back contact and right-hand armature of relay 523 and thence to ground through the lower right-hand and upper left-hand contacts of sequence :swi-tch spring-506 (l Belay 522 iS thereupon the lower left-hand contact 'quence switch spring 502 (1).

energized; and, at its left-hand armature and front contact, closes a locking circuit for contact upon which it is then resting to ground at the back contact, and outerrighthand armature of relay 400 of a primary line finder, provided such primary finder has not been placed in operation by a callingline. At its right-hand armature and front contact, relay 522 establishes a circuit for the stepprngsmagnet 526 which maybe traced from grounded battery, through the winding and interrupter contacts of magnet 526, through of sequence switch spring 508 (1), through the front contact and right-hand armature of relay 522, through the lower'left-hand contact or sequence switch spring 503 (1), through the front contact and left-hand armature of relay 521 and thence to ground through se- Stepping magnet 526 energizes in this circuit, stepping the brushes of the switch into contact with the next set of bank terminals and at its interrupter contacts opens its own circuit. If the next set of terminals leads to a primary switch which is in a non-calling condition, the relay 522 will continue in a locked condition and the circuit of the stepping magnet will again be established. The switch will therefore continue to move step-by step over its bank terminals until the test brush 525 engagesthe test terminal extending to the primary finder switch which has been started by the calling line, when no ground potential will be found on the test terminal, since the relay 400, of such switch has removed the ground potential at its outer right-hand armature and back contact. Relay 522 now becomes deenergized and at its left-hand armature and back contact connects ground potential through the test brush 525 to the multiple test terminals connected with the primary switch which has been seized and appearing in the banks of all secondary line finders which have access thereto for preventing seizure of the'same primary finder by other secondary finders. At the time relay 524 energized, it also closed a locking circuit for itself extending from grounded battery, through its winding and right-hand armature contacts, through the winding of relay 523, through the front contact and left-hand armature of relay 521 and thence to ground at sequence switch contact 502 (1). Relay 523 is energized in this circuit and, at its left-hand armature and back contact, opens the initial energizing circuit of relay 524, and its right-hand armature and back contact, opens the initial energizing circuit of i right-hand now effective for'driving the sequence switch 500 out of'position 1 and into position 2.

springs 509 (1),

relay 523,

and left-hand armature of "through the lower left-hand contact of sequence switch spring504: (1), through the back contact and right-hand armature of relay 522,-t-hrough the lower left han'd con tact of sequence switch spring 503 (1), through the front contact and left-hand armature of relay'521, and thence to ground through the lower contact of sequence switch spring 502 (1). I

At the time relay 521energized a circuit was also established through the winding of relay 527 for starting the hunting movement of the register selector RS. This circuit may be traced from grounded battery, through the winding of relay527, through the back contact and right-hand armature of relay 528, through the left-hand contacts of sequence switch spring 510 (1), through the back contact and left-hand armature of relay 529, through the lower lefthand contact of sequence switch spring 511 (1 and 2),

and thence to ground at the front contact and right-hand armature of "relay-521. hie-- energizing, closes a circuit for the relay 529 which may; be traced from grounded battery, through the winding of relay 529, through the lower contact of sequence'switch spring 512 (1 and 2), through the front contact and right-hand armature of relay 527, and thence to ground at the make-before-break left-hand armature contacts of relay 528. If the wipers of the register selector RS are at this time resting lay 527, upon upon the multiples of a busy registering or switch controlling device, a locking circuit will be established for the relay 529 which extends through its winding and right-hand armature contacts, through the lower right hand contact of sequence switch spring 513 (1 to 3), through the brush 530, and thence over the busy bank contact upon which it is resting to ground at the upper left-hand contact of sequence switch spring 602 '(2 to 18). Relay 527, upon energizing, also closes a locking circuit for itself extending through its winding and left-hand armature contacts, through the winding of relay 528, and thence to ground at the front contact and right-hand armature of relay 521 or, if at this time the sequence switch has moved into position 2, to ground through the lower contacts of sequence switch spring 511. Relay 528 energizesin this circuit and, at its left-hand armature contact, opens the initial energizing circuit of the relay 529 and, at its right-hand armature and back contact,

opens the initial energizing circuit of relay 527. Relay-529, upon energizing, establishes a circuit for the stepping magnet 531 which Vmay'be' traced from grounded battery, through the winding and; interrupter contacts of the magnet 531, through the lower contacts of sequence switch spring 51 1, through the front contact and left-hand armature of relay 529, and thence to ground at the right-hand armature and front contact of relay 521 or, if the sequence switch 500 has moved to position 2, to ground at the lower right-hand contact of sequence switch spring 511.

'lv-Iagnet 531, upon energizing, moves the brushes of the switch RS one step into contact with the next succeeding set of bank terminals and opens its own energizing circuit. If the bank terminals upon which the switch-brushes now rest lead to a busy registering mechanism, the test brush 530 will again encounter ground potential upon the bank terminal upon which it rests and the locking circuit of relay 529 will be maintained and the stepping magnet 531 will again move the switch brushes to the next set of bank terminals. This operation continues until thetest brush 530 engages a bank terminal which is not grounded at the sequence switch spring 602 of the regis tering niechanism'to which it leads the sequence switch 600 of such idle registering mechanism being in position 1. The locking circuit of relay 529 is now open and the relay retracts its armatures. At its left-hand armature and front contact, the relay 529 opens the circuit of the stepping magnet 531 and, at this armature and back contact, closes a circuit for driving the sequence switch 500 out of position 2 and, under the influence of the master contact 501, into position -1. This circuit may be traced from grounded battery, through the magnet winding of sequence switch 500, through the upper left-hand contact of sequence switch spring 509 (2), through the front "contact and right-hand armature of relay 528,

through the left-hand contacts of sequence switch spring 510, through the back contact and left-hand armature of relay 529, and thence to ground at'the lower right-hand contact of sequence switch spring 511 (2). At its right-hand armature and back contact, relay 529 established, upon deenergizing, a circuit for maintaining busy ground potential upon the multiple test terminals appearing in the terminal banks of switches -RS, which circuit is maintained through position 3 of the sequence switch and may be traced from ground at the make contacts of the left-hand armature of relay 528, through the back contact and right-hand armature of relay 529, through the lower C ntact of sequence switch spring 513 (1 to 3) and thence through brush 530 to the test contact'of the bank upon which it is resting.

As soon as sequence switch 500 moved out or" position 1, the locking circuit through relays 523 and 524 was opened at the lower contact of sequence switch spring 502 and these relays thereupon released. As soon as the sequence switch moved out of position 2, the locking circuit for relays 527 and 528 was opened at the lower contacts of sequence switch spring 511. In position 2 of sequence switch 500, a circuit is closed for relay 405 (Fig.4) for cutting through an impulse circuit from the calling line, through the brushes pf the primary line finder PLF, oi" the secondary line finder SLF, and of the register selector RS to the line relay 613 of the selected registering mechanism. This circuit may be traced from grounded bat tery, through the winding-of relay 405, through the right-hand armature and front contact of relay 412, through the bank termi nal 532 and the brush of the secondary finder switch which is resting thereon, and thenceto ground at the right-hand contacts of sequence switch spring 503, and a locking circuit is also closed at this time over the circuit just traced and through the righthand winding of relay 412. Relay 4055 upon energizing, closes the impulse circuit previously mentioned, extending from the calling line to the selected registering mechanism which may betraced from grounded battery, through the right-hand winding of relay 613, through the contact of sequence switch spring 603, (1 to 17) through the bank con tact 533, a brush of the register selector RS resting thereon, through the lower contact of sequence switch spring 515 (2 to 9), over brush 534 and the bank contact on which it is resting, through the armature and front contact immediately above the winding of relay 405, through the brush 407 of the primary-line finder PLF and the bank terminal on which it is resting, thence over the calling subscribers line loop and through the contacts of the impulse sender S at the subscribers substation A and thence back over the bank terminal 408 of the primary line finder and the brush resting thereon, through the uppermost armature and front contact of relay 405, over the bank terminal 535 a brush of switch SLF resting thereon, through the lower contact of sequence switch spring 516 (2 to 9), through the brush 536 oi. switch RS and the bank terminal upon which it is resting, through the contact of sequence switch spring 604 (1 to 17), and thence to ground through the left-hand winding of relay 613. Relay 405 at its lowermost armature and back contact, opens the locking circuit through relays 401 and 402, which thereupon deenergize, and at its inner lower armature, connects battery potential through the resistance 409, over brush resting to ground through the cut-off relay 9, which thereupon energizes, cutting off the line relay 8, which in turn causes the de-- '65 410 and the bank contact upon which it is grounded battery through the relay 616,

through the lower left-hand and upper right-hand contacts of sequence switch spring 605 (1) and thence to ground at the right-hand armature of relay 614. Relay 616 is energized and at its right-hand armature andfront contact, closes a locking circuit for itself extending to ground at the right-hand armature and front contact of relay 614. This circuit is maintained during the sending of impulses to the registering mechanism and the control of the selector switches thereby. At its left-hand armature and front contact, relay 616 closesa circuit for driving the sequence switch 600 out of position 1 and into position 2, this circuit extending from grounded battery, through the magnet winding of sequence switch 600, through the right-hand contact of sequence switch spring 606 (1) and to ground at the lefthand armature of relay 616. In the second position of the sequence switch, ground potential is connected to the multiple test terminals corresponding to the selected registering mechanism appearing in the banks of all register selector switches RS having access thereto, from ground at the left-hand contact of sequence switch spring 602 (2 to 18). The subscriber may now begin dialing the number of the called line which he desires.

Setting the registering mccham'sm.

Under the assumption that the number of the desired line is 45689, the subscriber first sets his dial S for sending impulses corresponding to the digit 4, and upon release of the dial, the circuit above traced through relay 613 is interrupted five times. It is to be noted in this connection that the dial S is provided with numerals arranged in the order 0 to 9 and that therefore one more 1mpulse is always transmitted than indicated by the numeral dialed. Upon each interruption of the circuit, the relay 613 retracts left-hand contact its armature, thereby "closing a circuit extending through the stepping magnet of the first or district brush register member of the registering mechanism, which circuit may be traced from grounded battery, through the stepping magnet 617, through the lower contact of sequence switch spring 607 (2 and 3), through the winding of slow acting relay 615,through the left-hand armature and front contact of relay 614, and thence to ground at the back contact and lef -hand armature of relay 613. In re sponse to these impulses, the stepping magnet 617 moves the wipers 618, 619 and 620 five steps to the fifth set of bank contacts. Relay 615 was energized in the circuit through the stepping magnet 617 and, being slow to release, remains energized the transmission of the series of impulses. Upon its initial energization, it established a circuit for driving the sequence switch 600 out of position 2 and into position 3, this circuit extending from grounded battery, through the magnet winding of the Sequence switch, through the upper right-hand contact of sequence switch spring 608 (2), and to ground at the front contact and armature of relay 615. Upon the cessation of the first series of impulses, the slow relay 615 becomes deenergized and, at its armature and back contact, closes a circuit for driving the sequence switch 600 out of position 3 and into position 41. llhis circuit extends through the magnet winding of the sequence switch, through the upper left-hand contact of sequence switch 608 (3), and thence to ground atthe back contact and armature of relay 615.

In response to the operation of the sending dial for the second series of impulses corresponding to the second digit 5, the re lay 613 transmits a series of six impulses through the stepping magnet 621 of the second or district group register member of the registering mechanism, this circuit extending from grounded battery, through the winding of magnet 621, through the upper right-hand contact of sequence switch spring 607 (4 and 5), thence through the relay 615 and over the circuit previously traced to ground at the armature and back contact of relay 613. In response to this series of im pulses, the magnet 621 steps the wipers 622, 623 and 62% six steps into contact with the sixth set of terminals of their respective banks, and relay 615 which was energized in the stepping circuit, causes the sequence switch 600 to move into position 5 by virtue of the circuit previously traced, extending through the upper right-hand contact of sequence switch spring 603 a Upon cessation of the second series of impulses, relay 615 becomes deenergized and establishes a circuit, previously traced, through the upper of sequence switch spring 608 (5) for driving the sequence switch 600 during I out of position 8 and into position 9.

out of position 5 and into position 6. In response to the third series ofimpulses corresponding to the digit 6, the steppingmagnet 625 becomes energized over a circuit extending through its winding, through the upper left-hand contact of sequence switch spring 607 (6 and 7), through the winding of relay 615, and thence to ground at the back contact of relay'613, thereby stepping the wipers 626, 627, 628 and 629 of the third or hundreds register member of the registering mechanism into engagement with the seventh set of bank contacts Relay 615 energizes in the stepping circuit of magnet 625 and, at its armature and front contact, causes the sequence switch 600 to move out of position 6 and into position 7. Upon the cessation of the third series of impulses, the relay 615 is de-nergized and establishes a circuit for driving sequence switch 600 out of position 7 and into position 8. In a similar manner the stepping magnet 630 in response to the fourth digit 8 steps the wipers 631 and 632 of the fourth or tens register member of the-registering mechanism nine steps. The circuit for the magnet 630 extends through the lower left-hand contact of sequence switch spring 609 (8 and 9) and thence to ground at the armature and back contact of relay 613, over the circuit previously traced. Relay 615 energizes in this circuit, thereby driving sequence switch 600 Upon the cessation of this series of impulses, relay 615 retracts its armature, thereby causing sequence switch 600 to move out of position 9 and into position 10. The last series of impulses corresponding to the digit 9 causes the stepping magnet 633 to step the brushes can and 635 of the. fifth or! units register member of the registering mechanism ten steps into contact with the tenth set of bank contacts. The circuit ofmagnet 633 may be traced through the lower right-hand contact of sequence switch spring 609 (10 and 11), through the winding of relay 615 and thence to ground at the back contact of relay 613. Upon the energization of relay 615, in response to this series of impulses, a circuit is established for driving sequence switch 600 out ofposition 10 and into position 11, and upon thedeiinergization of relay 615, following the cessation of this series of impulses, it establishes a circuit for driving sequence switch 600 out of position 11 and into position 12. The number of the desired line which has been dialed by the calling subscriber is now completely set up on the registering mechanism.

Selection of idle main line finder.

As soon as sequence switch 600 moved out of position 1 and into position 2, a circuit was established for the relay 529 extending from g ounded battery, through the wind..-

ing of the relay, through the upper contact of sequence switch spring 512 (4), througl brush 537 of the register selector RS, over the bank contact upon which this brush is resting, through the upper left-hand contact of sequence switch spring 606 (2 to 12), and thence to ground at the left-hand armature and front contact of relay 616. Relay energizes in this circuit closing, at its righthand armature and front contact, a locking circuit for itself extending through the upper right-hand contact of sequence switch spring 513 1 to 10), through brush 537 and thence to ground over the circuit previously traced. At its left-hand armature and front contact a circuit is established for driving the sequence switch 500 out of position 1 and into position 5, which circuit may be traced from grounded battery, through the magnet winding of sequence switch 500, through the lower righthand contact of sequence switch spring 51 i (1 to 1), through the front con tact and left-hand armature of relay 529, and thence to ground at the lower righthand contact of sequence switch spring 511 1 to 18). In position 5, relay 522 again energizes over a circuit traced from grounded battery, through the winding of relay 522, and thence to ground through the left-hand contacts of sequence switch spring 506 Relay 522, at its left-hand armature and front contact, closes a locking circuit for itself which is effective if the test wiper 538 is resting upon a bank terminal corresponding to a busy line finder switch LF. This circuit may be traced from grounded battery, through the winding of relay 522 and its left-hand armature and front contact, through the lower right-hand and upper left-hand contacts of sequence switch spring 507, through brush 538 and the bank terminal upon which it is resting, and thence to ground at the lower righthand contact of sequence switch spring 102. At its right-hand armature and front contact, a circuit is closed for driving sequence switch 500 out of position 5 and into position 6. which circuit may be traced from grounded battery, through the magnet windinnof sequence switch 500, through the lower right-hand contact of sequence switch spring 508 (5), through the front contact and right-hand armature of relay 522. and thence to ground at the upper contact of sequence switch spring 503 (2 to 10). In position 6, the initial energizing circuit of relay 522 is broken at the left-hand contacts of sequence switch spring 506, but under the assumption that the brushes of switch FS are standing upon the multiple terminals of a busy line finder link, the relay 522 does not de'e'nergize. A circuit is now effective for the up drive magnet 539, which circuit extends from grounded battery, through the winding of magnet 539, through the upper contact of sequence switch spring 508 (6),

through the front contact and right-hand the test contact of the bank and the relay will remain energized, thereby main taining the circuit of the up-drive magnet 539. As soon as the brush 538 encounters a test contact of the bank upon which there is no ground potential, the locking circuit of relay 522 will be destroyed but relay 522 will continue to attract its armatures by reason of a second locking circuit extending through its winding, through the upper right-hand contact of sequence switch spring 505 to 6), through the segment 540 of the switch commutator 7,and thence to ground through the shaft wiper 541. This second locking circuit is maintained until the brush set 2 becomes properly cen' tered upon the set of bank terminals Which it is engaging, when the shaft wiper 5 11 will engage an insulating portion of the segment 5 10 and the relay 522 will thereupon become deenergized.

Upon de'ejnergizing, the circuit of the updrive magnet 539 is opened at the righthand armature and front contact of relay 522 and a circuit is established for driving the sequence switch 500 out of position 6 and into position 7, this circuit extending from grounded battery, through the magnet winding of sequence switch 500, through the lower right-hand contact of sequence" switch spring 504 (6), through the back contact and right-hand armature of relay 522 and thence to ground at the upper contact of sequence switch spring 503. At its left-hand armature and back contact relay 522 connects busy ground potential through contacts of sequence switch spring 507 to the multipled test contacts in the bank of switch FS to prevent seizure of the selected link by oth r switches FS.

A circuit is now established for the relay 123 Fig. 1, which may be traced from grounded battery, through the winding of relay 123, through the lower contacts of sequence' switch spring 103, through the bank contact and wiper 542 of switch FS, through the upper contacts of sequence switch spring 513, through wiper 537 of the switch HS and the bank contact upon which it is resting, through the upper left-hand contact of sequence switch spring 606, and thence to ground at the front contact and left-hand armature ofrelay 616. Relay 123 energizes in this circuit and at its left-hand armature and front contact closes a locking circuit for itself extending through the lower righthand contact of sequence switch spring 103 and thence to ground over the circuit pre viously traced. At its right-hand armature and front contact, relay closes a circuit extending through the upper right-hand contact of sequence switch spring 10 1 for driving the sequence switch 100 out of posi- :tion 1 and into position 2.

Upcrcttioa of main Zine finder.

1n position 2, a circuit is established for the relay extending from grounded battery, through the right-hand winding of this relay, through the lower right-hand contact of sequence switch spring 105, over a haul; contact of sequence FS, through brush an, through the upper right-hand contact of se quence switch spring 50 1: (7), through the back contact and right-hand armature of relay and thence to ground at the upper 7 contact of sequence switch spring 50-3. illelay 12-; energizes in this circuit and at its right-hand armature and front. contact establishes a circuit for the up-drive magnet 125 oiithe line tinder switch LF, this circuit extending from grounded battery, through the winding of magnet 125, through the lefthand contacts of sequence switch spring 105, and thence to ground at the front contact of relay 124;. The magnet is energized and thereby presses the depending portion of the switch shaft 1 against the constantly rotating rip-drive roller 3. The switch shaft 1, together with its brush sets 2, is thereupon drivenupwardly. Upon the initial upward movement of the switch shaft, the shaftwiper 126 engages the lower conducting portion of the segment 127 of the commutator 7 of the line finder Ll, whereby a circuit is established for the relay 527 (Fig. 5) which circuit may be traced from grounded battery, through the winding of relay 527, through the back contact and right-hand armature of relay 528, through the lower left-hand and upper right-hand contacts of sequence switch spring 510, through the brush of switch F5 and the bank terminal upon which it is resting, through the right-hand contact of sequence switch spring 107, through the connnutator segment 12? and the wiper 126, then in engagement there with, through the upper left-hand contact of sequence switch spring 106, and thence to ground at the front contact and right-hand armature of relay 124. Relay 527 energizes in this circuit and locks up over a circuit extending'through its left-hand armature and front contact, through the winding of relay 528, and thence to ground through the lower contacts of sequence switch spring 511. Re lay 528, however, does not energize in this circuit since its winding is shunted by ground'connection at the shaft wiper 126 of the line fiber over the circuit previously traced. If the calling subscribers line is located in the subgroup of lines terminating in the bank to which the first, lowermost brush set of the line finder L1 has access, then a circuit is established at this time for the relay 522 extending from grounded battery, through the winding of relay 522, through the upper left-hand contact of sequence switch spring 505 (7) ,through brush 54.5, and thence over the bank terminal N upon which it is resting to the junction point designated 1, and from the junction point through the front contact and right-hand armature of relay 527 and to ground at the left-hand armature contacts of relay 528. Relay is energized in this circuit and, at its right-hand armature and back contact, opens the energizing circuit of relay 121 which thereupon deenergizes and opens the circuit of the up-drive magnet 125. if, however, the calling suhscribers line is located in the fifth. subgroup of lines as we will now assume, the bank terminals N connected to primary line finders assigned to this subgroup would not-be connected to the junction point. 1 but to the junction point 5 and thereby, upon the energization of relay 527, no circuit would be effective for the relay and consequently the upward movement of the line tinder shaftcontinues.

As soon as the wiper 126 engages the first insulating portion of the'seginent 127, the shunt around relay 528 is removed and this relay energizes over the locking circuit of relay 527, thereby opening at its right-hand armature and back contact the initial energizing circuit of relay 527 and at its righthand armature and front contact closing a circuit for the relay 52 1 which extends from grounded battery, through the relay 52%, through the back contact and left-hand (1'- inature of relay 523, through the contacts of sequence switch spring 517, through the front contact and right-hand armature of relay 52S, and thence over the circuit previously traced to the segment 127, and as soon the shaft wiper 126 moves up off of the first insulating portion of the segment, to ground through the wiper 125 over the circuit previously traced. Relay 524:, upon energizing over this circuit, closes a locking circuit for itself extending through its armature and front contact, through the winding of relay 523, and thence to ground through the lower left-hand and upper right-hand contacts of sequence switch spring 503. Relay 523, however, does not energize over this circuit since its Winding is shunted at the wiper 126 so long as the wiper 126 engages the conducting portion of the segment 127. As soon however, as the wiper 126 has moved upwardly into con- I switch spring 503.

tact with the second insulating portion of the seg'ment127, this shunt is removed and the relay 523 energizes. Upon energizing: it opens the initial energizing circuit of relay 524 at its left-hand armature and back contact and at its left-hand armature and front contact closes a circuit for relay 522 which is effective as soon as the wiper 126 again engages a conducting portion of the segment 12?. This circuit may be traced from grounded. battery, through the winding of relay 522, through the upper lef hand contact of sequence switch spring 505, through brush 545 of switch SLF, over bank contact N, thence to the junction point 5, through the front contact and left-hand armature of relay 523, through the contacts of sequence switch spring 517,throughthefront contact and right-hand armature of relay 52S and thence over the circuit previously traced, through the segment 127 and shaft wiper 126 to ground at the'right-hand armature ai'idfront contact of relay 124. Relay 522, as previously described, now opens the circuit of relay 124 which in turn opens the circuit of the up-dri've magnet 125. Relay 522 also closes at its right-hand armature and front contact, a circuit for driving sequence switch 500 out of position 7 and into position 8, this circuit extending through the magnet winding of the sequence switch, through the lower righthand contact of sequence switch spring 508 (7), through the right-hand armature and front contact of relay 52 and thence to ground at the upper contact of sequence The switch shaft of the line finder LF has now been driven upwardly through five steps and has positioned the fifth set of brushes in such a position relative to the tripping finger 6 of the tripping spindle 5 that, upon energization of the tripping magnet 128, this set of brushes is conditioned to be tripped in readiness to be traversed over its corresponding bank of contacts, upon a subsequent upward movement of the switch shaft. Relay 124, upon deene rgizing, in addition to opening the circuit of the up-drive magnet 125, closes at its right-hand armature and back contact a circuit through the upper righthand contact of sequence switch spring 108 for driving sequence switch 100 out of po sition 2 and into position 3, in which position a circuit is closed through the tripping magnet 128 and thence to ground through the upper right-hand contact of sequence switch spring 109.

It is to be noted that five junction terminals numbered. 1 to 5 inclusive, are associated with the relays 523.524, 527 and 528 of the link circuit shown in Fig. 5 for connection with bank terminals N appearing in the secondary line finders SLF, these junctions being connected into the banks of the secondary line finders in such manner that the tripping of a particular brush set of the line finder LF is made dependent upon a connection through the primary and secondary line finders to a subgroup in which the calling line is located and which subgroup of lines is one of the three subgroups of thirty lines each to which the particular brush set of the line finder LF has access.

In position 3 of sequence switch 100, a circuit is closed for again energizing relay 124, which circuit extends through the winding of the relay, and thence to ground at the lower left-hand contact of sequence switch spring 105 Upon energizing, relay 124 establishes a circuit through its right-hand armature and front contact and through the upper left-hand contact of sequence switch spring 108 (3) for driving sequence switch 100 out of position 8 and into position 4. In position 4, the initial energizing circuit of relay 124 is broken but the relay is maintained energized over a locking circuit eX- tending through the resistance 129, through the left-hand contacts of sequence switch spring 110 (8 and 4), through the left-hand armature and front contact of relay 124, through the left-hand contact of sequence switch spring 107 (3 and 4), through the brush of switch FS, and thence to grounded battery through the lower lefthand contact of sequence switch spring 518. A circuit is now established for the updrive magnet 125- which may be traced through the winding of the magnet, through the left-hand contacts of sequence switch spring-106 (4), and thence to ground at the front contact and right-hand armature of relay 124. Magnet 125, upon energizin presses the depending portion of the switcli shaft 1 against the constantly rotating updrive roller 3, thereby causing the switch shaft to be driven upwardly and to traverse the tripped set of brushes 2 over the bank cont-acts of the subgroup of ninety lines in which the calling line is located. This upward movement of the switch shaft continues until the test brush 130 engages the test terminal 181 corresponding to the calling line which has initiated the movement of the line finder LF, when a shunt circuit will be established around the left-hand winding of relay 124 for causing the deenergization thereof. This shunt circuit may be traced from grounded battery at the left-hand lower contact of sequence switch spring 518, over the circuit previously traced to the left-hand winding of relay 124, and thence through the front contact and left-hand armature of this relay, through the left-hand contacts of sequence switch spring 111 (3 and 4), over brush 130 and the test terminal 131, over brush 411 of the primary line finder switch PLF which has established a connection with the terminals of the calling line, through the left-hand armature and front contact of relay 412, through the wiper 548 of the secondary switch ELF, and through the contacts of sequence switch spring 518 to grounded battery. If the line finder Ll before reaching the terminal 131 of the calling line A had en countered a test terminal oi another calling line oi the same subgroup, the shunt circuit around the winding of relay 124: would not have been established. It is therefore apparent that it is impossible for a line finder to make connection with the terminals of any calling line other than the calling line which is through the operation of the primary and secondary line finders, initiating the hunt ing movement of the line finder L1 Upon the establishment of the shunt around the winding of relay 124:, this relay becomes. deenergized and its right-hand armature and front contact opens the. circuit of the up-drive magnet 125 and at its righ hand armature and a circuit through the upper right-hand contact of sequence switch spring 108 for driving sequence switch 100 out of position a and into position 5. The relay 1% however, does not deeners'ize nnmediately upon the shunting out of its winding unless the brushes are properly centered upon the proper set of bank terminals since the relay 1% is held energized momentarily over a circuit extending through its right-hand winding, through the upper right-hand contact of sequence switch spring 105 (35; and 4), through the segment 132 of the commutator 7, through the brush 126, and thence to ground through the upper left-hand contact of sequence switch spring 106 1) and through the front contact and right-hand armature of relay 12 1. When the brushes are properly centered the wiper 126 engages an insulating portion of the seg1nent132 and this looking circuit becomes destroyed.

hen sequence switch 100 reaches position 1%} a circuit is closed from grounded battery, through the right hand contacts of se quence switch spring 111 and thence through brush 154i and to round throu h the winding of cut-oil relay 9. This circuit holds relay 9 energized and marks the multiple terminals of the calling line as busy. in position 5 of sequence switch 100, a circuit is established for driving sequence switch 500, Fig. 5, out of position 8 and into position 10. This circuit may be traced from grounded battery through the magnet winding oi sequence switch 500, through the lower left-hand contact of sequence switch spring 519. through brush of the finder selector hit, over the bank terminal upon which it is resting, through sequence switch contact 122 (5), and thence to ground at the back contact and right-hand armabaclr contact, establishes ture of relay 1241, A new impulse circuit is now established from the line of the calling subscriber through to the selected registering nice-ha. m, since sequence switch 100 is now in position 5 and sequence switch 500 is in position 10. This circuit may be traced from grounded battery through the righthand winding of relay 613, through the contact of sequence switch spring 603, over banlr'terininal of the switch RS, and the wiper resting thereon, over the upper contact of sequence switch spring 515 (9 and 10), through brush or the switch FS, over the bank terminal upon which it is resting, through the lower contact of sequence switch spring 112, through the wiper 133 of the line finder FL, over the subibers line loop and the impulse sender thereat, and thence back through the wiper of the tinder Lid, through the lower conof sequence switch spring 113, through wiper 5%? of the switch ES, through the upper contact of sequence switch spring (9 and 10), over brush 536 of switch through the contact of sequence switch Gila, and thence to ground through the lefthand vinding of relay 613.

The c lling subscriber, it he has not al-' ready finished dialing over the impulse ciri established throughrthe primary and secondary line finder switches, may continue to send 1' ever the circuit just traced t irough the wipers off the line finder Ll).

hen sequence switch 500 moves outoi' position 9, the locking circuit for relay 112 and the energizing circ it of relay 105 be-' come opened at sequence switch spring 502 and these relays thereupon deenergize. he deenergization of relay 4:05 restores the circus of the line finder PLF to normal condition in readiness for serving further calls in the subgroup oi lines. Busy potential is removed at sequence switch spring 502 from the multiple contacts of the primary line finder which appear in the banks or all secondary line'finders.

Gvcra-z'on of selector switches.

iorvi-elay 135 which may be traced from grounded battery, through the left-hand winding of: this relay, through the left-hand contacts of sequence switch spring 114, through the brush 5% of finder selector FS, through the rigl'it-hand contacts of sequence switch spring 510, through brush 5&9, through sequence switch spring 610 (2 to 12), through the armature and back contact of relay 710, through the stepping relay 711 of the sender (Fig. 7) and thence to the lower left-hand contact of sequence switch spring 702. If, at this time, the subscriber has dialed the firsttwo digits of the desired number, sequence switch 600 will CIT have moved into position 6, in which position a. circuit was established for driving sequence switch 700 out of position 1 and into position 2, this circuit being traced from grounded battery, through the magnet winding of sequence switch 700, through the upper right-hand contact of sequence switch spring 703, and thence to ground through the upper right-hand contact of sequence switch 602, and the circuit prepared for stepping relay 711 above traced becomes completed through the lower contacts 01 sequence switch spring 702. Relay 135, upon energizing, closes a locking circuit for it self extending through its winding through its left-hand armature and front contact to the sequence switch spring 114, and thence to ground at the lower right-hand contact of sequence switch spring 702, over the circuit previously traced. At its right-hand armature and front contact, relay 135 closes a circuit extending over the lower righthand contact of sequence switch spring 115 tor driving sequence switch 100 out of position 5 and into position 6.

In position 6, a circuit is established for the up-drive ma net 186 of the district switch DES, this circuit extending from grounded battery, through the magnet 136, through the lower contact of sequence switch spring 116 (G), and thence to ground at the trout contact of relay 135. Upon energizing, magnet 136 presses the depending portion of switch shaft 1 against the constantly rotating up-drive roller 3, thereby causing the switch shaft and the wipers carried thereby to be moved upwardly. Upon the engagement of the shaft wiper 137 with the first conducting portion of the commutator segment 158, a branch circuit is connected from ground to the fundamental circuit at a junction point "etween the winding of relay 135 and the winding of the stepping relay 711. This branch circuit may be traced from ground, through the upper right-hand contact of sequence switch spring 102, (11 to 9) through the wiper 137 and the segment 138, and thence to the junction point in the fundamental circuit, through the upper lefthand contact of sequence switch spring 117 and 6). As soon as this branch circuit is closed, stepping relay 11 becomes shunted and retracts its armature, the relay 135 however, being maintained energized. over the branch circuit previously traced. Upon the initial ener ization of stepping relay 711, a circuit was closed from grounded battery through the No. counting relay. through the back contact and'armature of No. 2 counting relay thence over the lear. No. 2 to the correspondinglead in the middle bank of the district register through the wiper 619 which has been set on the fifth contact of the register bank, through the lower right-hand contact of sequence switch spring 704;, through the lower left-hand contact of sequence switch spring 705, through the front contact and armature of relay 711, and thence to ground through the lower right-hand contact of sequence switch spring 706. Relay 2 is energized in this circuit and locked up over a circuit extending through its winding, through the winding of the No. 2 counting relay. through the front contact and armature of No. 2 relay, and thence to ground at the lower contact of sequence switch spring 707. No. 2 counting relay does not energize however in this circuit since its winding is shunted by the ground connection at the lower right-hand contact of sequence switch spring 706 which is connected thereto during the energization of the stepping relay 711. Upon the first deenergization of the stepping relay 711 as previously mentioned, when the shaft wiper 137 contacted with the first conducting por tion of the commutator 138', this shunt circuit around the No. 2 counting relay was removed and the relay energized. Continued upward movement of the switch shaft 01 the district switch DS again rele' 'ta-blishes a circuit through the stepping relay 711 which now causes the energization of the No. 1 counting relay over a circuit from grounded battery, through the winding of this countingreay, through the back contact and armature of No. 1 counting relay, through the front contact and armature of the No. 2 counting relay and thence to ground at the lower right-hand contact of sequence switch spring 706, over the circuit previously traced. The counting relays are thus successively energized in response to the movement of the shaft wiper 137 over the commutator segment 138 of the district selector DS until the last counting relay No. 0 energizes in parallel with relay 710v When this relay energizes a circuit is es tablished for driving sequence switch 700 out of position 2 and into position 4, this circuit being traced from grounded battery, through the magnet winding of the sequence switch, through the armature and front contact oi the 2's 0. O counting relay, and thence to ground at the upper contact'ot sequence switch spring 707'. The energization oi"relay 710 opens the it'undamental circuit through stepping relay 711 and through the relay 7 135 of the district selector. The switch shaftof the district selector has now been moved upwardly three steps, thereby positioning the third set of brushes having access to the twenty thousand line division of the exchange containing lines 40,000 to inclusive in a position to be tripped by the operation of the tripping spindle 5 during a subsequent upward movement oi the switch. shaft. Upon the deenergization '01: T 3 1 quence switch 100 is driven into osition T b a circuit extendin i y h 

